This invention relates to a method and apparatus for the manufacture of dead burnt materials such as clay, dolomite, magnesite or periclase to produce the highest particle specific gravity from each in a selected size range. More particularly, the present invention relates to an energy efficient improved method and apparatus for producing refractory grade dead burnt materials which utilizes a continuous process including a suspension-type preheater, a flash or suspension-type calcining system, a hot briquetting machine and a rotary sintering machine.
Prior to the present invention, it was known to produce dead burnt materials such as dolomite including the step of soft burning the raw material in a furnace such as a shaft furnace or rotary kiln at a temperature in the range of 1000.degree. to 1200.degree. C. Subsequent to the soft burning of the material, it is common practice to slake or hydrate the material by the addition of water to form hydroxide. Thereafter, the hydroxide may be formed into pellets or nodules in order to aid densification and then dead burned at a temperature on the order of 1300.degree. to 1800.degree. C. to sinter the material to produce the desired refractory grade specific gravity product. There may be a period of storage between the formation of pellets and the final sintering refractory grade materials. Typical of such processes are U.S. Pat. Nos. 1,912,894; 3,304,188; 3,698,922; and 3,736,161.
In such prior processes, typical fuel consumption is on the order of 12 to 14.times.10.sup.6 BTU's per ton of end product. It would be useful to be able to produce a similar product having a reduced fuel consumption while maintaining product quality.